Accused “Dark Knight” killer James Holmes was formally charged Monday with two first-degree murder counts for each of the 12 people fatally shot during Colorado’s movie theater rampage.

The dual charges -- 24 counts in all -- break down as “murder with deliberation” and killing with “extreme indifference to the value of human life.” That allows the prosecution two paths in pursuing a possible death sentence should Holmes mount a successful insanity defense, NBC News reported.

"Dark Knight" Massacre Trial Will Be Lengthy

"Dark Knight" massacre suspect, James Holmes, made his first public appearance in court on Monday. The District Attorney discusses the charges, possibility of the death penalty, and the lengthy trial to come. (Published Tuesday, July 24, 2012)

Murder with deliberation covers premeditated murder while extreme indifference to the value of human life covers actions that show “an attitude of universal malice,” NBC News reported.

Holmes was also charged with 116 counts of attempted murder in the shooting which wounded 58 people, as well as one count of possession of explosives.

Aurora, Colo., Cinema Rampage Remembered

Police say the 24-year-old former doctoral student booby-trapped his suburban Denver apartment with explosives before opening fire on theatergoers for the July 20 premiere of the new Batman film. Authorities later removed the explosives during a painstaking operation.

Holmes appeared less dazed during his court appearance Monday than he had for last week's advisement hearing, according to reports. His dyed red hair was slicked down his head, The New York Times reported. Unlike the first appearance, cameras were barred from the courtroom.

Holmes is being held in solitary confinement at a detention facility about 13 miles from Aurora's Century 16 theaters, site of the killings.

Last Monday, police and FBI agents recovered a package sent by Holmes to the University of Colorado medical school, which contained writings about killing people. Authorities found the package in the school's mailroom after acting on a tip from Holmes, NBC News reported.

Lawyers were expected to argue at today's hearing over a defense motion to find out who leaked information about the package to the media, the AP reported.

Meanwhile, court documents filed Friday by defense lawyers showed that Holmes was a patient of a University of Colorado psychiatrist before the attack.

Holmes allegedly set off gas canisters in the early minutes of "The Dark Knight Rises," then sprayed the room with bullets while dressed all in black and outfitted in body armor and a gas mask. Witnesses said that at first they mistook the gunman for a planned part of the show — but then “mass chaos” broke out. Amid the terror, there emerged stories of heroism: theatergoers who sacrificed themselves to protect their loved ones. Holmes was arrested outside the theater with four guns, all purchased legally, and told police he was the Batman villain "the Joker."

Holmes' hair was still dyed red and orange at his initial appearance in court last week. He appeared dazed and gave little indication that he was paying attention to the proceedings. The hearing lasted no more than 12 minutes before he was led out of the courtroom in handcuffs.

The appearance marked the first step in what will likely be a years-long slog through the criminal justice system, including exhaustive reviews of his mental health.

Lawyers’ first big legal hurdle is to determine whether Holmes is competent to stand trial – that he understands the charges against him, and that he can assist in his own defense.

That process alone can take months. If he’s found incompetent, he must be sent to a state mental hospital for treatment.

“Virtually everyone initially found to be incompetent is at some point found to be restored to competency,” said Patrick Furman, a University of Colorado law professor. The rare exceptions, he said, typically come in cases in which the defendant is severely developmentally disabled.

When and if Holmes is deemed by a judge to be fit for trial, then his lawyers will likely plead not guilty by reason of insanity, setting in motion many more months of legal proceedings, Furman said.

Holmes could face the death penalty, but District Attorney Carol Chambers said such a decision would be made in consultation with victims' families.